The nonpartisan Massachusetts Taxpayers Foundation, in the study released on Tuesday, said the liability threatens to wreak havoc with local government and place crushing burdens on property taxpayers in the future.

“If these benefits aren’t reigned in in some way, (it) means one of two things: that services will continue to be cut for cities and towns and/or that the finances of these cities will just hit the wall and they’ll go effectively bankrupt,” Foundation executive director Michael Widmer told WBZ NewsRadio 1030.

The foundation says the $20 billion estimate is likely understated given the steep rise in health care costs.

The report says the unfunded liability for health insurance is about 2 1/2 times greater than the more well-publicized unfunded pension liability.

The foundation recommends several actions, including giving local officials power to adjust health plans outside of collective bargaining.